The parliament in South Africa is currently reviewing a secrecy bill that will makewhistleblowers or journalists who possess, leak or publish state secrets liable to 25 years in prison. JM Coetzee, Nadine Gordimer, Desmond Tutu, even Nelson Mandela's lawyer George Bizos, have lined up to condemn the bill as an insult, something worthy of the apartheid-era laws on state secrecy that the ANC fought so hard to dismantle. Mr Mandela's views are not known, but his foundation has said the law could be yet struck down by the constitutional court. The Congress of South African Trade Unions stands ready for the challenge.

Faced with a reaction on this scale, the ANC has backed off, a bit. It has improved protection for whistleblowers in one clause, but has not budged on its opposition to a public-interest defence for the meat of the bill – espionage, or more loosely "hostile activities", which would "directly or indirectly" benefit a foreign state. Mere possession of such information remains a crime, and even if the information is already in the public domain, five years in prison awaits those who do not hand it in to the police. Had this bill been law when the ANC's greatest scandal – the receipt of £100m of bribes in an arms deal – was uncovered by former ANC MP Andrew Feinstein, he might never have found a publisher to print his book.

South Africa is still a vibrant democracy with the freest press in the continent. Even the bill's most ardent opponent, the civil society alliance Right2Know, acknowledges the revisions to which the law has been subject. The sword may well be sheathed in its final form, but the real question is still how Jacob Zuma will wield it.

The ANC has long since stopped being the party of Mr Mandela or Walter Sisulu. Nor is it indeed that of Thabo Mbeki, whose own relationship with the press soured, but who never gagged it. If critics are right to talk of the emergence of a paranoid securocratic cadre of leaders under Mr Zuma, then this bill spells trouble, even if it is watered down.

After 18 years of incumbency, the ANC is losing its "liberation dividend", with a generation born after its first free election and Mr Mandela's release. Inequalities are growing and more than half of 18- to 25-year-olds are unemployed. The masses are leaderless and their leaders are corrupt and self-serving. A mighty firewall of state secrets will not protect Mr Zuma and the ANC if they fail to deliver. The former ANC security chief may be tempted to establish a regime where loyalty to his leadership trumps any other. But he would surely be wiser to acknowledge the ANC's real position – that it is no longer the vanguard of a revolution, but only one party among others. He would be wiser to heed the warnings of his country's many remaining democrats.